Effect of Self-Interstitial Diffusion Anisotropy in Electron-Irradiated Zirconium. A Cluster Dynamics Modeling

2005 ◽  
Vol 237-240 ◽  
pp. 659-664
Author(s):  
Frédéric Christien ◽  
Alain Barbu
Keyword(s):  
Point Defects ◽  
Thin Foil ◽  
Elastic Interaction ◽  
Dislocation Loops ◽  
Considerable Influence ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Diffusion Anisotropy ◽  
Vacancy Loops ◽  
Transmission Electron

Irradiation of metals leads to the formation of point-defects (vacancies and selfinterstitials) that usually agglomerate in the form of dislocation loops. Due to the elastic interaction between SIA (self-interstitial atoms) and dislocations, the loops absorb in most cases more SIA than vacancies. That is why the loops observed by transmission electron microscopy are almost always interstitial in nature. Nevertheless, vacancy loops have been observed in zirconium following electron or neutron irradiation (see for example [1]). Some authors proposed that this unexpected behavior could be accounted for by SIA diffusion anisotropy [2]. Following the approach proposed by Woo [2], the cluster dynamics model presented in [3] that describes point defect agglomeration was extended to the case where SIA diffusion is anisotropic. The model was then applied to the loop microstructure evolution of a zirconium thin foil irradiated with electrons in a high-voltage microscope. The main result is that, due to anisotropic SIA diffusion, the crystallographic orientation of the foil has considerable influence on the nature (vacancy or interstitial) of the loops that form during irradiation.

Study of dislocation loops in Arsenic-Rich as-grown GaAs

1987 ◽  
Vol 45 ◽  
pp. 350-351
Author(s):  
Byung-Teak Lee
Keyword(s):  
Point Defects ◽  
Electronic Devices ◽  
Arsenic Concentration ◽  
Stoichiometric Compound ◽  
Dislocation Loops ◽  
Gaas Crystal ◽  
Ion Milling ◽  
Transmission Electron ◽  
Arsenic Source ◽  
High Arsenic

Grown-in dislocations in GaAs have been a major obstacle in utilizing this material for the potential electronic devices. Although it has been proposed in many reports that supersaturation of point defects can generate dislocation loops in growing crystals and can be a main formation mechanism of grown-in dislocations, there are very few reports on either the observation or the structural analysis of the stoichiometry-generated loops. In this work, dislocation loops in an arsenic-rich GaAs crystal have been studied by transmission electron microscopy.The single crystal with high arsenic concentration was grown using the Horizontal Bridgman method. The arsenic source temperature during the crystal growth was about 630°C whereas 617±1°C is normally believed to be optimum one to grow a stoichiometric compound. Samples with various orientations were prepared either by chemical thinning or ion milling and examined in both a JEOL JEM 200CX and a Siemens Elmiskop 102.

Point Defect Detector Studies of Ge+ Implanted Silicon upon Oxidation

1992 ◽  
Vol 262 ◽  
Author(s):  
H. L. Meng ◽  
S. Prusstn ◽  
K. S. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Point Defect ◽  
Point Defects ◽  
Type Ii ◽  
Dislocation Loops ◽  
Furnace Annealing ◽  
Plan View ◽  
Atom Concentration ◽  
Transmission Electron

ABSTRACTPrevious results [1] have shown that type II (end-of-range) dislocation loops can be used as point defect detectors and are efficient in measuring oxidation induced point defects. This study investigates the interaction between oxidation-induced point defects and dislocation loops when Ge+ implantation was used to form the type II dislocation loops. The type II dislocation loops were introduced via Ge+ implants into <100> Si wafers at 100 keV to at doses ranging from 2×1015 to l×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. The change in atom concentration bound by dislocation loops as a result of oxidation was measured by plan-view transmission electron microscopy (PTEM). The results show that the oxidation rate for Ge implanted Si is similar to Si+ implanted Si. Upon oxidation a decrease in the interstitial injection was observed for the Ge implanted samples relative to the Si implanted samples. With increasing Ge+ dose the trapped atom concentration bound by the loops actually decreases upon oxidation relative to the inert ambient implying oxidation of Ge+ implanted silicon can result in either vacancy injection or the formation of an interstitial sink.

Dislocations around scratches and indents on ±(111) surface of gallium arsenide

1989 ◽  
Vol 22 (6) ◽  
pp. 606-612 ◽  
Author(s):  
M. R. Surowiec ◽  
H. S. Leipner ◽  
J. Schreiber
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Point Defects ◽  
Nucleation Mechanism ◽  
Dislocation Loops ◽  
X Ray ◽  
Transmission Electron ◽  
Double Kink ◽  
Slip Planes ◽  
Scanning Electron

The dislocation configurations around microscratches and indents on ±(111) surfaces of GaAs single crystals were studied by X-ray transmission topography, scanning electron microscopy in cathodoluminescence mode and high-voltage transmission electron microscopy. Most of the dislocations generated are loops of screw – B(g) or screw –B(g) – screw character gliding on {111} slip planes parallel or inclined to the surface. The irregular shape of the extended loops gliding parallel to the B surface is due to interaction with other loops and apparent motion involving a double kink nucleation mechanism. The exhibited configuration of dislocation loops suggests a cross-slip orientation of the dissociated screw segments. The direction of propagation of dislocations does not depend on the sense of scratching. Grown-in dislocations are surrounded by a cloud of point defects and they are immobile in contrast to dislocations introduced by indentation.

Effect of the End of Range Loop Layer Depth on the Evolution of {311} Defects.

1998 ◽  
Vol 532 ◽  
Author(s):  
R. Raman ◽  
M. E. Law ◽  
V. Krishnamoorthy ◽  
K. S. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Experimental Investigation ◽  
Point Defects ◽  
Chemical Mechanical Polishing ◽  
Dislocation Loops ◽  
Layer Depth ◽  
Plan View ◽  
Projected Range ◽  
Transmission Electron

ABSTRACTThe interactions between end of range dislocation loops and {311} defects as a function of their proximity was studied. The dislocation loops were introduced at 2600 Å by a dual 1 × 1015 cm−2, 30 keV and a 1 × 1015 cm−2 , 120 keV Si+ implantation into Silicon followed by a anneal at 850 °C for 30 minutes. The depth of the loop layer from the surface was varied from 2600 Å to 1800 Å and 1000 Å by polishing off the Si surface using a chemical-mechanical polishing (CMP) technique. A post-CMP 1 × 1014 cm−2, 40 keV Si+ implantation was used to create point defects at the projected range of 580 Å. The wafers were annealed at 700, 800 and 900 °C and plan-view transmission electron microscopy (TEM) study was performed. It was found that the number of interstitials in {311} defects decreased as the projected range damage was brought closer to the loop layer, while the number of rectangular elongated defects (REDs) increased. Experimental investigation showed that REDs are formed at the end-of-range. It is concluded that the interstitials introduced at the projected range are trapped at the end-of-range dislocations. The REDs are formed due to the interactions between the interstitials and the pre-existing loops.

Elastic interaction of dislocation loops and point defects

1964 ◽  
Vol 14 (6) ◽  
pp. 443-453 ◽  
Author(s):  
J. Baštecká ◽  
F. Kroupa
Keyword(s):  
Point Defects ◽  
Elastic Interaction ◽  
Dislocation Loops

Defect clustering in GaN irradiated with O+ ions

2002 ◽  
Vol 17 (11) ◽  
pp. 2945-2952 ◽  
Author(s):  
C. M. Wang ◽  
W. Jiang ◽  
W. J. Weber ◽  
L. E. Thomas
Keyword(s):  
Point Defects ◽  
Basal Plane ◽  
Room Temperature ◽  
Dynamic Recovery ◽  
Stacking Faults ◽  
Extended Defects ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Transmission Electron ◽  
High Resolution Tem

Transmission electron microscopy (TEM) was used to study microstructures formed in GaN irradiated with 600-keV O+ ions at room temperature. Three types of defect clusters were identified in the irradiated GaN: (i) basal-plane stacking faults with dimensions ranging from 5 to 30 nm, (ii) pyramidal dislocation loops, and (iii) local regions of highly disordered material. High-resolution TEM imaging clearly revealed that one type of the basal-plane stacking faults corresponded to insertion of one extra Ga–N basal plane in the otherwise perfect GaN lattice. The interpretation of these results indicated that interstitials of both Ga and N preferentially condensed on the basal plane to form a new layer of Ga–N under these irradiation conditions. The formation of these extended defects and their interactions with the point defects produced during irradiation contributed to a dramatic increase in the dynamic recovery of point defects in GaN at room temperature.

Xenon Ion Irradiation Effects on a Ni-Base Ni-17Mo-7Cr Alloy

2014 ◽  
Vol 94 ◽  
pp. 69-74 ◽  
Author(s):  
He Fei Huang ◽  
De Hui Li ◽  
Long Yan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
Base Alloy ◽  
Thin Foil ◽  
Dislocation Loops ◽  
Irradiation Effects ◽  
Transmission Electron ◽  
Black Spots ◽  
Nickel Base

The irradiation effects of a new nickel-base alloy (Ni-17Mo-7Cr) has been investigated by using 1 MeV Xe20+ and 7 MeV Xe26+ ions irradiation with displacement damage range from 0.33 to 6.6 dpa. The transmission electron microscopy and nanoindentation were employed to study respectively the microstructural evolution of thin-foil specimens and nanoindentation hardness changes of bulk specimens. In case of 0.33 dpa, high number density of nano-scale black spots were observed in thin-foil specimens. High-resolution transmission electron microscopy images revealed that these black spots are some rounded solute clusters and dislocation loops. As far as the ion dose of 3.3 and 6.6 dpa, the black spots were replaced with linear-like defects which were proved to be some Ni, Mo and Cr-enrichment regions. In addition, nanoindentation results for bulk specimens showed an evident hardening phenomenon in irradiated Ni-17Mo-7Cr alloys, compared to the unirradiated specimen. The irradiation induced defects may be responsible for the hardening of Ni-17Mo-7Cr alloys.

Point Defect Detector Studies of Oxidized Silicon

1991 ◽  
Vol 238 ◽  
Author(s):  
H. L. Meng ◽  
K. S. Jones ◽  
S. Prussin
Keyword(s):  
Ion Implantation ◽  
Point Defect ◽  
Point Defects ◽  
Device Fabrication ◽  
Type Ii ◽  
Dislocation Loops ◽  
Plan View ◽  
Atom Concentration ◽  
Enhanced Diffusion ◽  
Transmission Electron

ABSTRACTIon implantation and thermal oxidation are device fabrication processes that lead to perturbation of equilibrium point defects concentration in silicon. This study investigates the interaction between oxidation-induced point defects and type II dislocation loops intentionally introduced in silicon via ion implantation. The type II dislocation loops were introduced via Si implants into (100) Si wafers at 50 keV to a dose ranging from 2×1015 to 1×1016/cm2. The subsequent furnace annealing at 900 °C was done for times between 30 min and 4 hr in either a dry oxygen or nitrogen ambient. Plan-view transmission electron microscopy (PTEM) was used to characterize the increase in atom concentration bound by dislocation loops as a result of oxidation. The results show type II dislocation loops can be used as point defect detector and they are efficient in measuring oxidation-induced point defects. It is also shown that the measured net interstitials flux trapped by dislocation loops is linearly proportional to the total supersaturation of interstitials as measured by oxidation enhanced diffusion (OED) studies.

scholarly journals Transmission Electron Microscopy Study In-Situ of Radiation-Induced Defects in Copper at Elevated Temperatures

1996 ◽  
Vol 439 ◽  
Author(s):  
T. L. Daulton ◽  
M. A. Kirk ◽  
L. E. Rehn
Keyword(s):  
Point Defects ◽  
Elevated Temperatures ◽  
Defect Density ◽  
Microscopy Study ◽  
High Energy ◽  
Dislocation Loops ◽  
Contrast Imaging ◽  
High Concentration ◽  
Transmission Electron

AbstractNeutrons and high-energy ions incident upon a solid can initiate a displacement collision cascade of lattice atoms resulting in localized regions within the solid containing a high concentration of interstitial and vacancy point defects. These point defects can collapse into various types of dislocation loops and stacking fault tetrahedra (SFT) large enough that their lattice strain fields are visible under diffraction-contrast imaging using a Transmission Electron Microscope (TEM). The basic mechanisms driving the collapse of point defects produced in collision cascades is investigated in situ with TEM for fcc-Cu irradiated with heavy (100 keV Kr) ions at elevated temperature. The isothermal stability of these clusters is also examined in situ.Areal defect yields were observed to decrease abruptly for temperatures greater than 300°C. This decrease in defect yield is attributed to a proportional decrease in the probability of collapse of point defects into clusters. The evolution of the defect density under isothermal conditions appears to be influenced by three different rate processes active in the decline of the total defect density. These rate constants can be attributed to differences in the stability of various types of defect clusters and to different loss mechanisms. Based upon observed stabilities, estimations for the average binding enthalpies of vacancies to SFT are calculated for copper.

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